mm/page_owner.c: add missing __initdata attribute

This patch fixes two issues:
1. Add __initdata attribute according to include/linux/init.h:
	For initialized data:
	You should insert __initdata between the variable name and equal
	sign followed by value

2. Fix below error reported by checkpatch.pl:
	ERROR: do not initialise statics to false

Special thanks to Muchun Song :)

Link: https://lkml.kernel.org/r/20220516030039.1487005-1-bh1scw@gmail.com
Signed-off-by: Fanjun Kong <bh1scw@gmail.com>
Suggested-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>